JP6188357B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device that controls an internal combustion engine mounted on a vehicle.

  In an internal combustion engine mounted on a vehicle, it is known to perform a fuel cut that interrupts fuel injection in accordance with the operation state (see, for example, Patent Document 1 below). Normally, when the accelerator pedal depression amount is 0 or less than a threshold value close to 0 and the engine speed is equal to or higher than the fuel cut permission speed, the fuel cut is started assuming that the fuel cut condition is satisfied. Then, when any fuel cut end condition is satisfied, such as when the accelerator pedal depression amount exceeds the threshold value, or the engine speed decreases to the fuel cut return speed, the fuel cut ends and the fuel injection resumes. .

  Recently, it has also become common to implement an idle stop that stops the idle rotation of the internal combustion engine while the vehicle is stopped due to a signal waiting or the like (see, for example, Patent Document 2 below). In the known idling stop system, the internal combustion engine is stopped when various conditions such as the vehicle speed is lower than a predetermined value, the brake pedal is depressed, and the coolant temperature and the battery voltage are sufficiently high are satisfied. After idling stop, when the driver makes a restart request such as releasing the brake pedal or depressing the accelerator pedal, or when the length of the idling stop period exceeds a predetermined value, restart the internal combustion engine. Start.

  When the driver removes his or her foot from the accelerator pedal while the vehicle is running and the vehicle decelerates and stops, first the fuel cut condition is satisfied and the fuel cut is started, and then the engine shifts to idle stop. However, it does not mean that no fuel is injected between the start of fuel cut and the idle stop. Actually, the fuel cut end condition is satisfied when the vehicle speed drops to about 10 km / h, and fuel injection is temporarily resumed. Then, the idle stop condition is established at a vehicle speed of about 9 km / h, and the fuel injection is stopped again, whereby the internal combustion engine and the vehicle are further decelerated to idle stop and stop.

  Temporary fuel injection that occurs between the fuel cut and idle stop is a factor that deteriorates the effective fuel consumption. Therefore, the vehicle speed condition, which is one of the idle stop conditions, is raised. For example, when the vehicle speed is 13 km / h or less (assuming that other conditions are satisfied), the fuel cut is performed by permitting the idle stop. It is conceivable to consistently continue from to idle stop.

Japanese Patent Laid-Open No. 10-030477 JP 2012-137018 A

During fuel cut without fuel injection, air containing no fuel component flows from the cylinder into the exhaust purification catalyst via the exhaust passage. Therefore, catalyst occluded a large amount of oxygen, the reduction ability of the NO _x by the catalyst is reduced. When idle stop in such a state is carried out, there is a concern that emissions of the NO _x is increased at the restart of the internal combustion engine.

The present invention, while achieving further improvement in fuel economy, and the intended purpose of suppressing the emission of the NO _x in the restart after idle stop of the internal combustion engine.

  In order to solve the above-described problems, in the present invention, a fuel cut that temporarily stops fuel injection is performed when a predetermined fuel cut condition is satisfied, and idle rotation of the internal combustion engine is performed when a predetermined idle stop condition is satisfied. When the fuel cut condition is satisfied and the fuel cut is started, and the idle stop condition is satisfied and the idle stop is started, it is captured by the fuel evaporative emission control device. The control device for the internal combustion engine is configured to execute purge control for flowing the fuel vapor flowing into the exhaust purification catalyst.

The purge control is preferably executed on the condition that the length of the period from the end of the fuel cut to the start of the idle stop is counted and the length of the period is equal to or less than a predetermined value. That is, the length of the period becomes an index value that indicates the amount of oxygen stored in the catalyst at the start of idle stop (and at the end of idle stop). When the length of the period is equal to or less than a predetermined value, it means that the amount of stored oxygen is equal to or greater than a predetermined value. Increases NO _x purification efficiency at the time.

Note that the length of the period may be zero. This corresponds to the case where the idle stop condition is satisfied before the fuel cut end condition is satisfied during the fuel cut, and the fuel cut to the idle stop is continuously continued without interposing the temporary restart of the fuel injection. In the purge control, the length of time for opening the control valve provided on the flow path connecting the fuel evaporative emission control device and the intake passage of the internal combustion engine or the opening of the control valve is large. It is also preferable that the upper limit of the depth be smaller as the cooling water temperature is higher or smaller as the intake air temperature is higher .

According to the present invention, while achieving further improvement in fuel economy, emissions of the NO _x in the restart after idle stop can be suppressed.

The figure which shows schematic structure of the internal combustion engine in one Embodiment of this invention. The flowchart which shows the example of the procedure of the process which the control apparatus of the internal combustion engine of the embodiment implements.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of an internal combustion engine for a vehicle in the present embodiment. The internal combustion engine in the present embodiment is a spark ignition type 4-stroke gasoline engine, and includes a plurality of cylinders 1 (one of which is shown in FIG. 1). In the vicinity of the intake port of each cylinder 1, an injector 11 for injecting fuel is provided. A spark plug 12 is attached to the ceiling of the combustion chamber of each cylinder 1. The spark plug 12 receives spark voltage generated by the ignition coil and causes spark discharge between the center electrode and the ground electrode.

  The intake passage 3 for supplying intake air takes in air from the outside and guides it to the intake port of each cylinder 1. On the intake passage 3, an air cleaner 31, an electronic throttle valve 32, a surge tank 33, and an intake manifold 34 are arranged in this order from the upstream.

  The internal combustion engine is accompanied by a fuel evaporative emission control device. The universal fuel evaporative emission control device is called a charcoal canister. The fuel vapor evaporated in the fuel tank is adsorbed and captured by the canister 35 filled with activated carbon, and the fuel vapor is sent to the intake passage 3 at appropriate times. This is mixed with intake air and burned in the cylinder 1.

  The canister 35 is connected to a predetermined portion (surge tank 33 or intake manifold 34) downstream of the throttle valve 32 in the intake passage 3. On the flow path connecting the canister 35 and the intake passage 3, a purge VSV (Vacuum Switching Valve) 36, which is a control valve for opening and closing the flow path, is provided. While the VSV 36 is opened, the canister 35 and the intake passage 3 communicate with each other through the flow path, and the fuel vapor in the canister 35 is drawn into the intake passage 3 by the intake negative pressure generated downstream of the throttle valve 32. It is.

  The exhaust passage 4 for discharging the exhaust guides the exhaust generated as a result of burning the fuel in the cylinder 1 from the exhaust port of each cylinder 1 to the outside. An exhaust manifold 42 and an exhaust purification three-way catalyst 41 are disposed on the exhaust passage 4.

  An ECU (Electronic Control Unit) 0 serving as a control device for an internal combustion engine according to the present embodiment is a microcomputer system having a processor, a memory, an input interface, an output interface, and the like.

  The input interface includes a vehicle speed signal a output from a vehicle speed sensor that detects the actual vehicle speed of the vehicle, a crank angle signal b output from an engine rotation sensor that detects the rotation angle and engine speed of the crankshaft, and depression of an accelerator pedal. An accelerator opening signal c output from a sensor that detects the amount or the opening of the throttle valve 32 as an accelerator opening (engine output required by the driver, so-called required load), and output from a sensor that detects the amount of depression of the brake pedal Indicating the brake pedaling amount signal d, the intake air temperature / intake pressure signal e output from the temperature / pressure sensor for detecting the intake air temperature and the intake pressure in the intake passage 3 (particularly, the surge tank 33), and the temperature of the internal combustion engine The coolant temperature signal f output from the coolant temperature sensor that detects the coolant temperature to be detected, the intake camshaft or the exhaust camshaft The cam angle signal g output from the cam angle sensor at the cam angle, the battery current (or voltage) indicating the charge state of the in-vehicle battery, the battery status signal h output from the sensor detecting the battery temperature, and the like are input. Is done.

  From the output interface, an ignition signal i for the igniter of the spark plug 12, a fuel injection signal j for the injector 11, an opening operation signal k for the throttle valve 32, an opening / closing control signal l for the purge VSV 36, and the like. Output.

  The processor of the ECU 0 interprets and executes a program stored in the memory in advance, calculates operation parameters, and controls the operation of the internal combustion engine. The ECU 0 acquires various information a, b, c, d, e, f, g, and h necessary for operation control of the internal combustion engine via the input interface, knows the engine speed, and is filled in the cylinder 1. Estimate the intake volume. Based on the engine speed, the intake air amount, and the like, various operation parameters such as required fuel injection amount, fuel injection timing, fuel injection pressure, and ignition timing are determined. The ECU 0 applies various control signals i, j, k, and l corresponding to the operation parameters via the output interface.

  Further, the ECU 0 inputs a control signal o to the electric motor (starter motor or motor generator) when the internal combustion engine is started (a cold start or a return from an idling stop). Cranking is performed by rotating the crankshaft. Cranking ends when the internal combustion engine starts from the first explosion to a continuous explosion and the engine speed, that is, the rotation speed of the crankshaft, exceeds a judgment value determined according to the coolant temperature, etc. (assuming that the explosion has been completed) To do.

  The ECU 0 of the present embodiment performs a fuel cut that temporarily stops the fuel supply to the cylinder 1 in accordance with the driving situation. In addition, the ECU 0 also performs an idle stop for stopping the idle rotation of the internal combustion engine when the vehicle stops due to a signal waiting or the like.

  FIG. 2 shows a procedure example of processing executed by the ECU 0 when the vehicle decelerates and stops. When a predetermined fuel cut condition is satisfied (step S1), the ECU 0 performs fuel cut that stops fuel injection from the injector 11 and stops spark ignition by the spark plug 12 (step S2). In step S1, it is determined that the fuel cut condition is satisfied, at least when the accelerator pedal depression amount is 0 or less than a threshold value close to 0 and the engine speed is equal to or higher than the fuel cut permission speed.

  Incidentally, even if the fuel cut condition is satisfied, the fuel injection is not immediately stopped. If the fuel supply is cut off suddenly when the engine torque is relatively large, a torque shock that causes the engine speed and the vehicle speed to drop stepwise occurs, causing the passengers including the driver to feel the shock. In order to reduce the torque shock, the fuel injection is stopped only after the elapse of the delay time after the fuel cut condition is satisfied. During this delay time, the ignition timing is retarded and the engine torque is actively reduced.

  When a predetermined fuel cut end condition is satisfied after the start of fuel cut and before an idle stop condition described later is satisfied (step S3), the fuel cut is ended and fuel injection (and ignition) is resumed. (Step S4). In step S3, it is determined that the fuel cut end condition is satisfied, for example, when the amount of depression of the accelerator pedal exceeds a threshold value or the engine speed decreases to the fuel cut return speed.

  In addition, when a predetermined idle stop condition is satisfied (steps S6 and S8), the ECU 0 executes an idle stop that stops the idle rotation of the internal combustion engine (steps S10 and S11). In Steps S6 and S8, all conditions were satisfied that the vehicle speed was not more than a predetermined value (for example, a value of 10 km / h to 13 km / h), the brake pedal was depressed, and the coolant temperature and battery voltage were sufficiently high. Therefore, it is determined that the idle stop condition is satisfied.

  After the fuel cut is started, if the fuel cut end condition is not satisfied and the idle stop condition is satisfied (step S8), the fuel injection is not resumed, and the state is shifted to the idle stop with the fuel cut state (step S11). )

Therefore, after the fuel cut is performed, the ECU 0 opens the VSV 36 and sends the fuel vapor captured by the canister 35 to the intake passage 3 when the idle stop condition is satisfied and the idle stop is started. 1 is prohibited, and purge control is performed to cause the gas containing unburned fuel vapor to flow into the catalyst 41. Purge control, during the fuel cut by consuming the occluded oxygen in the catalyst 41, to promote the reduction reaction of the NO _x when the restart after idle stop, is intended for suppressing emission of the NO _x .

  The ECU 0 acquires an index value indicating the amount of oxygen stored in the catalyst 41 immediately before starting the idle stop (step S5). In this step S5, for example, the length of the period from the temporary resumption of fuel injection accompanying establishment of the fuel cut end condition to the start of idle stop accompanying establishment of the idle stop condition is counted. Is an index value indicating the amount of occluded oxygen. The length of the period is the elapsed time or the number of rotations of the crankshaft. It can be understood that the shorter the period, the greater the amount of oxygen stored in the catalyst 41.

  Then, based on the index value indicating the amount of stored oxygen, it is determined whether or not the oxygen stored in the catalyst 41 needs to be purged (step S7). Specifically, when the length of the period from the satisfaction of the fuel cut end condition to the satisfaction of the idle stop condition counted in step S5 is equal to or less than a predetermined value, it is determined that the stored oxygen needs to be purged. I will give you. In the case where the idling stop condition is satisfied during the fuel cut (step S8) and the fuel cut (step S2) to the idling stop (step S11) are continuously continued without interposing the temporary resumption of fuel injection, the above period It is determined that it is necessary to purge the stored oxygen.

If it is recognized that the stored oxygen needs to be purged, purge control is executed after the idle stop condition is established (step S9). As already described, in the purge control step S9, the VSV 36 is opened, the spark ignition by the spark plug 12 is stopped, and the gas containing fuel vapor flows into the catalyst 41 via the cylinder 1 and the exhaust passage 4. . The unburned fuel vapor that has flowed into the catalyst 41 reacts (oxidizes or burns) with the oxygen stored in the catalyst 41. Thus, oxygen stored in the catalyst 41 is reduced is consumed increases the reduction efficiency of NO _x.

  The purge control is allowed to be executed immediately after the idle stop condition is established. In order to suck the fuel vapor from the canister 35 into the intake passage 3, the intake negative pressure on the downstream side of the throttle valve 32 is used. Therefore, the purge control needs to be performed while the internal combustion engine is rotating. In the present embodiment, the purge control step S9 is executed before the engine rotation is stopped by the idle stop. However, it is impossible to execute this when restarting after the idle stop (during cranking, etc.). is not.

  The length of time for opening the VSV 36 in the purge control step S9 and / or the size of the opening of the VSV 36 are set according to the cooling water temperature and / or the intake air temperature of the internal combustion engine at that time. This is intended to prevent the fuel vapor from self-igniting and explosive combustion in the combustion chamber of the cylinder 1 or in the exhaust passage 4. Therefore, the upper limit of the valve opening time and / or opening of the VSV 36 is decreased as the cooling water temperature is higher, and is decreased as the intake air temperature is higher.

  Incidentally, the valve opening time and / or the opening degree of the VSV 36 in the purge control step S9 may be adjusted according to the index value indicating the stored oxygen amount obtained in step S5. Specifically, the shorter the period from when the fuel cut end condition is satisfied to when the idle stop condition is satisfied, the longer the valve opening time of the VSV 36 or the larger the opening of the VSV 36. If the above period is long, it is considered that the oxygen storage amount of the catalyst 41 at the start of idling stop is sufficiently reduced. Therefore, the purge control is effectively executed by setting the valve opening time or opening of the VSV 36 to 0. It is possible not to.

  The purge control ends when the required valve opening time of the VSV 36 has elapsed (step S15) or when the rotation of the internal combustion engine has stopped (the engine speed has become 0 or less than a threshold value close to 0) (step S15). S16).

  After the idle stop condition is satisfied, when the predetermined idle stop end condition is satisfied (steps S12 and S13), the internal combustion engine is restarted (step S14). In steps S12 and S13, a predetermined time (for example, 3 minutes) has elapsed in an idle stop state in which the driver has lifted his foot from the brake pedal, conversely, the brake pedal has been further depressed, or the accelerator pedal has been depressed. From any of the above, it is determined that the idle stop termination condition is satisfied.

  When the idle stop termination condition is satisfied before the purge control is completed, the purge control is interrupted (VSV 36 is closed), and the internal combustion engine is immediately restarted. In this restart, an amount of fuel necessary for starting is injected from the injector 11 of each cylinder 1 and spark ignition by the spark plug 12 of each cylinder 1 is permitted.

  In the present embodiment, a fuel cut that temporarily stops fuel injection is performed when a predetermined fuel cut condition is satisfied, and an idle stop that stops idle rotation of the internal combustion engine is performed when a predetermined idle stop condition is satisfied. The fuel vapor trapped by the fuel evaporative emission control device 35 is exhausted when the idle stop condition is satisfied and the idle stop is started after the fuel cut condition is satisfied and the fuel cut is started. The control device 0 for the internal combustion engine that executes purge control for flowing into the purification catalyst 41 is configured.

According to the present embodiment, when shifting to the idle stop after the fuel cut, excess oxygen stored in the catalyst 41 during the fuel cut can be digested, so NO in restarting the engine after the idle stop It becomes possible to suppress the discharge of _x . As in this embodiment, the vehicle speed condition, which is one of the idle stop conditions, is raised (for example, to 10 km / h to 13 km / h), and the temporary fuel injection period from the end of the fuel cut to the start of the idle stop is increased. Even if the period is shortened or the period is eliminated and the engine is shifted to the idling stop while the fuel is cut, the deterioration of the emission is avoided. Therefore, it contributes to further improvement of fuel consumption performance.

  Unlike the fuel injected from the injector 11, the fuel vapor captured by the fuel evaporative emission control device 35 is less likely to adhere to the inner wall of the intake port (port wet). That is, unburned fuel components can be reliably sent to the catalyst 41 during the purge control, and variations in the air-fuel ratio of the intake air charged in the cylinder 1 when the internal combustion engine is restarted are unlikely to occur (port wet). Can avoid the phenomenon of vaporizing and enriching the air-fuel ratio).

In addition, in this embodiment, the length of the period from the end of the fuel cut to the start of the idle stop is counted, and the purge control is executed on the condition that the length of the period is equal to or less than a predetermined value. . Only when it is considered that the amount of oxygen stored in the catalyst 41 is larger than the predetermined limit and needs to be purged, the VSV 36 is opened and fuel vapor is supplied, so that NO _x emission is suppressed. However, fuel consumption can be saved, and the combustion can be stabilized when the engine is restarted.

  The present invention is not limited to the embodiment described in detail above. The index value indicating the oxygen storage amount of the catalyst 41, which is a material for determining whether or not the purge control needs to be executed, is not limited to the length of the period from the end of the fuel cut to the start of the idle stop. For example, the length of the fuel cut period performed immediately before the idle stop, that is, the length of the period from the start of the fuel cut to the end of the fuel cut, or the start of the fuel cut (the end of the fuel cut) The length of the period until the idle stop condition is satisfied (without the condition being satisfied) may be counted and handled as an index value that suggests the amount of oxygen stored in the catalyst 41. In this case, purge control is executed on condition that the counted length of the period is equal to or less than a predetermined value.

  It is conceivable that the total amount of intake air flowing into the catalyst 41 during the fuel cut is counted to estimate the amount of oxygen stored in the catalyst 41, and purge control is executed on the condition that the amount of oxygen is greater than or equal to a predetermined value. . The amount of intake air charged into one cylinder 1 in one intake stroke can be estimated based on the pressure in the surge tank 33 and the engine speed at that time, and the amount of intake air is integrated over the fuel cut period ( (Or time integration), the total amount of intake air flowing into the catalyst 41 is obtained. It goes without saying that the amount of oxygen stored in the catalyst 41 increases as the total amount of intake air that flows into the catalyst 41 during the fuel cut increases.

  There is an upper limit to the oxygen storage capacity of the catalyst 41, and the amount of oxygen stored by the catalyst 41 during fuel cut does not exceed the oxygen storage capacity. The oxygen storage capacity of the catalyst 41 decreases as the catalyst 41 deteriorates over time. The ECU 0 appropriately estimates the oxygen storage capacity of the catalyst 41 as diagnosis. In estimating the amount of oxygen occluded in the catalyst 41 during the fuel cut, and thus in determining whether or not the purge control needs to be executed, the oxygen occlusion capability may be taken into consideration.

  In the diagnosis of the catalyst 41, the air-fuel ratio of the gas flowing into the catalyst 41 is forcibly made lean in a situation where oxygen is completely released from the catalyst 41, and then the output of the air-fuel ratio sensor downstream of the catalyst 41. The amount of oxygen currently stored in the catalyst 41 is estimated by measuring the elapsed time until the signal switches to lean. The oxygen storage amount at the moment when the output signal of the air-fuel ratio sensor downstream of the catalyst 41 reverses lean becomes the maximum oxygen storage capacity of the catalyst 41.

  Alternatively, under a situation where oxygen is stored in the catalyst 41 to the maximum oxygen storage capacity, the air-fuel ratio of the gas flowing into the catalyst 41 is forcibly made rich, and then the output signal of the air-fuel ratio sensor downstream of the catalyst 41 is By measuring the elapsed time until switching to rich, the amount of oxygen released by the catalyst 41, that is, the oxygen storage amount based on the state in which oxygen is stored to the full oxygen storage capacity can be estimated. The oxygen storage amount at the moment when the output signal of the air-fuel ratio sensor downstream of the catalyst 41 is richly inverted becomes the maximum oxygen release capacity of the catalyst 41, that is, the maximum oxygen storage capacity.

  The contents of the fuel cut condition and the idle stop condition are not limited to those in the above embodiment, and can be changed as appropriate. Similarly, the contents of the fuel cut end condition and the idle stop end condition may be changed as appropriate.

  In addition, the specific configuration of each unit, the processing procedure, and the like can be variously modified without departing from the spirit of the present invention.

  The present invention can be applied to control of an internal combustion engine mounted on a vehicle.

0 ... Control unit (ECU)
DESCRIPTION OF SYMBOLS 1 ... Cylinder 11 ... Injector 12 ... Spark plug 35 ... Fuel evaporative-gas emission suppression apparatus (canister)
41 ... Catalyst

Claims (2)

Implementing a fuel cut that temporarily stops fuel injection when a predetermined fuel cut condition is established, and performing an idle stop that stops idle rotation of the internal combustion engine according to the establishment of a predetermined idle stop condition,
After the fuel cut condition is satisfied and the fuel cut is started, when the idle stop condition is satisfied and the idle stop is started, the fuel vapor captured by the fuel evaporative emission control device flows into the exhaust purification catalyst. and performing a purge control to,
A control device for an internal combustion engine, which counts a length of a period from the end of the fuel cut to the start of the idle stop, and executes the purge control on condition that the length of the period is equal to or less than a predetermined value . Implementing a fuel cut that temporarily stops fuel injection when a predetermined fuel cut condition is established, and performing an idle stop that stops idle rotation of the internal combustion engine according to the establishment of a predetermined idle stop condition,
After the fuel cut condition is satisfied and the fuel cut is started, when the idle stop condition is satisfied and the idle stop is started, the fuel vapor captured by the fuel evaporative emission control device flows into the exhaust purification catalyst. Execute purge control to
In the purge control, the length of time for opening the control valve provided on the flow path connecting the fuel evaporative emission control device and the intake passage of the internal combustion engine or the size of the opening of the control valve A control apparatus for an internal combustion engine, wherein the upper limit is made smaller as the cooling water temperature is higher or smaller as the intake air temperature is higher .

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